A software license is a legal instrument governing the usage or redistribution of software. A typical software license grants an end-user permission to use one or more copies of software. There are several types of software licenses. One type of software license is freeware (sometimes referred to as shareware). Freeware software is created by an author and put into the public domain; there are no copyright restrictions. Freeware can be copied and distributed freely. Shareware is copyrighted software that the developer encourages you to copy and distribute. This permission is explicitly stated in the documentation. The developer usually requests a registration fee if you like the software and plan to use it. Registering the software usually ensures that program and documentation updates are sent to you.
Another type of software license is a Limited License (LL). An LL is an agreement whereby software is purchased with limits and/or restrictions on the number of copies available for installation or use. LL's are sometimes limited to a designated number of computers (up to the number of group copies purchased) or as many users operating a program at any given time as the number of concurrent copies purchased. Some LL's for educational institutions are restricted to use in connection with on-campus computing facilities that are used solely in support of classroom instruction and research activities of students, teaching faculty and staff, and research staff.
Another type of software license is an Unlimited Site License (USL). A USL is an agreement whereby software is purchased with no limit on the number of copies available for installation. USL's are sometimes limited to specific people (such as state-funded faculty and staff). The only cost that an individual or department may have to bear is the cost of burning a CD and/or purchasing documentation. Some USL's are available for checkout, usually for one to three days, others are downloadable via the Internet. Documentation for some USL's may be found on limited loan in the Library's Reserve Book Room or in PDF format on the Internet.
Yet another type of software license is referred to as desktop license/perpetual license. This type of software license permanently binds the license to customer's system. A customer can transfer the license to another system by explicitly deactivating the software from first system and then provisioning the second system. Still another type of software license is known as online service license, wherein a user always need to be connected with a backend licensing system in order to use the entitled products/services.